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STRENGTH ASSESSMENT

By: Matt Brzycki

Brzycki is the coordinator of health, fitness, strength and conditioning
programs at Princeton University. He has authored three books, co-authored
another and written more than 180 articles on strength and fitness for 33
different publications.

Strength tests are used for a variety of populations, from professional
athletes to recreational

fitness enthusiasts. The main
reasons for performing strength tests are to evaluate initialstrength
levels and to assess changes in strength. Regardless of the reason for testing
muscular strength, trainers and other staff need to perform testing in a safe,
efficient manner. Examined here are some traditional forms of strength testing,
as well as some alternate ways to test to ensure accuracy and the test's safety.

The history of strength assessments

Strength tests and measurements began in the U.S. around 1860. At that time,
the major focus was on anthropometric measurements, such as size and symmetry.
Around 1880, physical testing shifted from anatomical proportions to muscular
strength. Then, in the 1920s, new and more scientific test methods were
developed, and statistical techniques for data analysis became available.
Through the years, a few specific types of strength tests have become the most
popular.

Traditional 1-RM testing requires skill, proper warm-up,
instruction,

supervision and practice.

Traditional test methods

Two basic types of strength tests have evolved: static and dynamic. In a
static (or isometric) test, a muscle exerts tension against a fixed, nonmoving
resistance. In a dynamic (or isotonic) test, one or more body parts moves
against a resistance.

Strength testing has gradually become more sophisticated. Now tests can be
conducted in a formal, scientific setting - such as a laboratory or sports
medicine facility with equipment ranging from relatively simple dynamometers and
tensiometers to more elaborate isokinetic and motor- driven testing devices.
Some equipment can even provide both static and dynamic tests that measure
strength at different joint angles over a full range of motion, and then plot a
"strength curve" with an incredible degree of accuracy. Unfortunately,
such scientific testing can be expensive and involves a considerable amount of
time. In addition, sophisticated scientific tests are usually not practical to
assess a large number of individuals.

Fortunately, there is a more convenient way to assess muscular strength
without the drawbacks of elaborate scientific testing. Since these easier
assessments are performed outside of a formal scientific setting, they are
referred to as "field tests." Field tests represent simple,
convenient, easy-to-administer methods of measurement that require a minimum
amount of time, cost and equipment. For these reasons, many strength and fitness
professionals rely on field tests to assess muscular strength.

The most popular (and traditional) way to assess dynamic strength is to
determine how much weight an individual can lift for one repetition. A
one-repetition maximum (1- RM) is usually performed using three or four
exercises that are representative of the body's major muscle groups. For
example, a bench press or an incline press is typically used to assess the
strength of the chest, shoulders and triceps, while a squat or a leg press is
often used to measure the strength of the hips and legs.

Traditional 1-RM testing

The traditional way to test strength using a 1-RM raises a number of
concerns. One reservation is that performing a 1-RM is a highly specialized
skill, requiring proper warm-up, instruction, supervision and practice.1
In addition, traditional1-RM testing can be
time-consuming, due to the number of warm-up sets that are required to prepare
for the maximal attempt. These problems are magnified when evaluating a large
group of people. 1,2

Another concern with traditional1-RM testing is an increased risk of
musculoskeletal injury.

l,2,3,4
Attempting a 1-RM with a maximal or near-maximal weight can place an inordinate
amount of stress on muscles, bones and connective tissues. Injuries occur when
the stress exceeds the tensile strength of these structural components. The
concern for safety increases when testing certain populations, such as younger
adolescents and older adults who are at greater risk for orthopedic injury.1

Fitness professionals must identify a means to assess the muscular strength
of their clients that is safe and efficient, but also inexpensive, practical and
reasonably accurate.

Strength and anaerobic endurance

To discuss alternate ways to test strength, it's necessary to distinguish
between strength and anaerobic endurance. In basic terms, strength is the
ability to exert force, and maximal strength is a measure of the ability to
exert force during a single muscular contraction with a maximal load. In
contrast, anaerobic endurance is the ability to exert force during successive
muscular contractions with a submaximal load. It is important not to confuse
anaerobic endurance with cardiovascular endurance. Anaerobic endurance is a
short-term, high-intensity muscular effort---less than about two minutes;
cardiovascular endurance involves muscular effort for a much longer duration.

Strength and anaerobic endurance are highly related.

4
A review of strength-training literature indicates that there is a direct
relationship between reps-to-fatigue and the percentage of maximal load (or
weight): As the percentage of maximal load increases, the number of repetitions
decreases in an almost linear fashion.5

Data also suggests that 10 reps-to-fatigue could be performed with a weight
equal to approximately 75 percent of a maximal load.

5
For example, if your 1-RM is 200 pounds, then you should be able to perform 10
reps-to-fatigue with 150 pounds (75 percent of 200). Expressed in other terms,
if your maximal strength is 200 pounds, then a measure of your anaerobic
endurance is your ability to perform 10 repetitions with 150 pounds before
experiencing muscular fatigue. This would also be known as your 10-repetition
maximum (10-RM).

Unless you have an injury or other musculoskeletal disorder, the relationship
between your muscular strength and your anaerobic endurance remains relatively
constant.

4
Therefore, regardless of whether your strength increases or decreases, you
should always be able to perform the same number of repetitions with a given
percentage of your 1-RM. This also suggests that if you improve your 1-RM by 20
percent, then your 10-RM should also improve by 20 percent. Conversely, if you
increase your anaerobic endurance, then you also increase your muscular
strength. So, if you improve your 10-RM by 20 percent, then your 1-RM should
also improve by 20 percent. Keep in mind, however, that the actual improvement
in a 1-RM may be less if you haven't practiced the requisite skill in performing
a 1-RM.

Implications for testing

Since there is a direct relationship between anaerobic endurance and
strength, you can determine anaerobic endurance by measuring strength, and
determine strength by measuring anaerobic endurance. Though it doesn't directly
measure pure maximal strength, testing anaerobic endurance is much safer than
attempting a 1-RM because it involves submaximal loads.

A number of prediction equations have been developed and used to estimate a
1-RM based on the relationship between strength and anaerobic endurance. While
some of the equations have proven to be reasonably accurate, one problem with
them is that they do not take into consideration individual differences.

2,3

Genetic influences on testing Each individual inherits a different potential
for improving muscular size and strength, cardiovascular' endurance, anaerobic
endurance and other physical attributes. Indeed, a person's physical profile is
largely determined by several inherited characteristics, including the ratio of
fast-twitch (FT) to slow-twitch (ST) muscle fibers, limb length and neurological
ability.

Because of these genetic influences, especially muscle fibers, some people
perform either less than or more than 10 reps-to-fatigue with 75 percent of
their maximal strength. Westcott reported data on 141 subjects who did a test of
anaerobic endurance with 75 percent of their 1-RM.

6
(Remember, it has been suggested that an individual could do 10 reps-to-fatigue
with this workload.) According to the data, the subjects completed an average of
10.5 repetitions. However, only 16 of the 141 subjects (11.35 percent) did
exactly 10 reps-to-fatigue with 75 percent of their 1-RM. Many of the subjects
were within a few repetitions of 10. In fact, 66 of the subjects (46.81 percent)
were able to do between eight and 13 reps-to-fatigue. On the other hand, 75 of
the subjects (53.19 percent) did either less than eight reps-to-fatigue or more
than 13. At the extremes, two subjects did only five reps-to-fatigue and one
managed 24.

If predicting a 1-RM from reps-to-fatigue is to be as accurate as possible,
individual differences in anaerobic endurance must be considered. There are
several ways to determine an individual-specific estimate of a 1-RM.

1-RM and anaerobic endurance tests.

One way to obtain an individual-specific estimate of a 1-RM is to perform
actual tests of muscular strength and anaerobic endurance. To do this, first
determine the maximal weight that you can lift for one repetition using good
technique. Next, assess your anaerobic endurance by taking 75 percent of your
1-RM and performing as many repetitions as possible using good technique. For
instance, if your 1-RM is 200 pounds, do a set with 150 pounds (75 percent of
200). Suppose that you are able to do eight reps-to-fatigue with 75 percent of
your 1- RM (instead of 10 reps-to-fatigue as has been suggested). You have just
established an individual-specific relationship between your strength and
anaerobic endurance based upon your inherited characteristics. More
specifically, you now know that you can do eight reps-to-fatigue with 75 percent
of your 1-RM. In the future, you can estimate your 1-RM based upon your
inherited characteristics by dividing the most weight you can lift for eight
repetitions by 0.75.

A two-set prediction equation.

Another approach to attain an individual-specific estimate of a 1-RM is to
use a prediction equation. The most frequently used prediction equations are
based on the reps-to-fatigue done in one set.

2,3
However, a test using one set does not account for individual differences in
anaerobic endurance. A better way to assess muscular strength from anaerobic
endurance is to use a prediction equation that is based on the reps-to-fatigue
obtained in two sets. A two-set prediction equation is shown in Figure 1.

To illustrate the equation, guesstimate a weight that will allow you to reach
muscular fatigue in approximately four or five repetitions. On a later date,
guesstimate a weight that will allow you to reach muscular fatigue in
approximately nine or 10 repetitions. It doesn't really matter how many
repetitions you do in the two sets, as long as you do not exceed 10. Now,
suppose that you did five reps with 165 pounds in the first set and 10 reps with
135 pounds in the subsequent set. Inserting these values into the equation
yields an individual-specific predicted 1-RM of 189 pounds.

l-RM graphing method

A final way to make an individual-specific estimate of a 1-RM is to use a
graph and plot the reps-to-fatigue obtained in two sets. On a sheet of graph
paper, draw a vertical line down the left-hand side of the page. Starting at the
bottom of this vertical line, draw a horizontal line across the page. Label the
vertical line "weight" and mark off five- or 10-pound increments;
label the horizontal line "reps-to-fatigue" and mark off 10
increments, numbering them from one to 10. The intervals between the numbers on
both lines must be equidistant.

Once the graph is set up, perform two sets with the same guidelines as
previously stated. On the graph, plot the weight that you used and the number of
reps-to-fatigue that you did in both sets. Using a ruler, connect these two
points and extend this line to the left until it intersects the vertical line
that designates one repetition. This extrapolation is an individual-specific
estimate of your 1-RM.

An application of the graphing method appears in Figure 2. In this instance,
consider again that you did 5 reps with 165 pounds and 10 reps with 135 pounds.
When these two points are plotted on the graph and the line is extrapolated to
the left, it yields a predicted 1-RM of 189 pounds---the same maximum that was
estimated by the two-set prediction equation.

Implications for training

There is not currently any consensus on the percentage of maximal weight that
is necessary to stimulate optimal gains in strength. For the moment, however,
imagine that it is 75 percent. According to the study by Westcott, this workload
appears to allow an average of about 10 reps-to-fatigue.

6
Recall, though, that his data also showed that many individuals can do either
less than or more than 10 reps-to-fatigue. These individual differences in
anaerobic endurance suggest the need to customize repetition ranges to maximize
the response to strength training. For example, those who cannot do more than 10
reps-to-fatigue with 75 percent of their 1-RM have a relatively low level of
anaerobic endurance (and likely a high percentage of fast-twitch muscle fibers).
These individuals would benefit more by training with slightly lower repetition
ranges. Conversely, those who can do more than 10 reps-to-fatigue with 75
percent of their 1-RM have a relatively high level of anaerobic endurance (and
likely a high percentage of slow-twitch muscle fibers). These individuals would
benefit more by training with slightly higher repetition ranges. This is not to
say that 75 percent is the optimal workload for stimulating increases in
strength. The use of 75 percent of a 1-RM is only to illustrate the point about
the need for individualized repetition ranges.

There are also implications for pre-planned or "periodized"
workouts that demand specific numbers of repetitions with certain percentages of
a 1-RM. For instance, a workout might requite individuals to perform 10
repetitions with 75 percent of their 1-RM. Because of wide variations in
anaerobic endurance, however, such a prescription might be far too easy for some
and literally impossible for others. Therefore, pre-planned workout schedules
that stipulate the same number of repetitions with a specific percentage of
maximal load for everyone may be minimally effective, except for the segment of
the population who have a particular level of anaerobic endurance that
corresponds exactly to the specifications and parameters of the training
prescription.